Eden

Contents

First, you must do Priscilla's first two quests: Give her Water Materia and Tiara of the Deep. Then, kill Ultima Weapon. After this, talking with her again will make give the quest The Strongest Eidolon. Talking with her again will make her summon Eden. You have around 12 minutes to destroy it. After this, you may continue to fight Eden as much as you want by talking with Priscilla.

Currently, defeating Ultima Weapon before the completion of Priscilla's first quest (See above) will render you unable to activate Priscilla's second quest (The Strongest Eidolon) and thus, you won't be able to fight Eden, which will render you unable to defeat him. He will not appear at the Tower of Summoning (quest) and you won't be able to summon Dark Eden (Dark Eden is needed to finish the Dark Eidolon quest to fight against Penance).